Power saving with adaptive inactivity time out

Abstract

Power saving for wireless communication devices by adjusting the amount of time, after a last transmission/reception of data, that the device remains in an awake mode listening for more data before the device enters a sleep mode. This time period may be referred to as inactivity time interval or inactivity timeout (ITO). The described features may be employed to improve power savings by taking metrics of channel congestion into account for determining the ITO. The appropriate ITO may be determined to be commensurate with ongoing transmission and/or reception activity. Because error may occur in estimating channel congestion and/or transmission/reception activity, latency bounds based on estimation errors may be managed by classifying the operational mode into multiple regions and employing techniques for mitigating error in congestion estimation based at least in part on the operational mode.

What is claimed is: 
     
       1. A method performed by a device of a wireless communications network, comprising:
 communicating with an access point of the wireless communications network during awake intervals in which the device is in an awake mode; 
 determining a running average of at least one channel congestion metric of at least one channel of the wireless network during a first awake interval of the awake intervals; 
 determining, for at least one awake interval of the awake intervals, an inactivity time interval for remaining in the device awake mode after at least one uplink or downlink transmission of the at least one awake interval based at least in part on the determined running average of the at least one channel congestion metric; and 
 adjusting the inactivity time interval for the device for at least one from the group consisting of: 
 the first awake interval, and 
 a subsequent awake interval. 
 
     
     
       2. The method of  claim 1 , wherein determining the running average of the channel congestion metric comprises:
 determining a block average of a number of preceding determinations of the channel congestion metric. 
 
     
     
       3. The method of  claim 1 , wherein determining the running average of the channel congestion metric comprises:
 determining a weighted average of a number of preceding determinations of the channel congestion metric. 
 
     
     
       4. The method of  claim 1 , wherein
 the at least one channel congestion metric is based at least in part on transmission activity on the at least one channel other than by the device. 
 
     
     
       5. The method of  claim 1 , wherein
 the at least one channel congestion metric is based at least in part on reception activity on the at least one channel other than by the device. 
 
     
     
       6. The method of  claim 1 , wherein
 the at least one channel congestion metric is based at least in part on transmission and reception activities on the at least one channel other than by the device. 
 
     
     
       7. The method of  claim 1 , wherein determining the inactivity time interval based at least in part on the determined running average of the at least one channel congestion metric comprises:
 accessing a look-up table that includes a plurality of values of the at least one channel congestion metric and a corresponding plurality of inactivity time interval values; 
 identifying a value of the plurality of values based at least in part on the running average of the at least one channel congestion metric; and 
 selecting one of the plurality of inactivity time interval values corresponding to the identified value. 
 
     
     
       8. The method of  claim 1 , wherein determining an inactivity time interval based at least in part on the determined running average of the at least one channel congestion metric comprises:
 accessing a look-up table that includes a plurality of values of the at least one channel congestion metric and a corresponding plurality of inactivity time intervals for each of a plurality of access classes; 
 identifying a value of the plurality of values based at least in part on the running average of the at least one channel congestion metric; 
 identifying an access class currently being used by the device; and 
 
       selecting one of the plurality of inactivity time intervals corresponding to the identified value and the identified access class. 
     
     
       9. The method of  claim 1 , further comprising:
 entering a sleep mode after an elapse of the determined inactivity time interval; and 
 polling the access point of the wireless network during a sleep mode interval to determine if data is to be transmitted to the device from the access point. 
 
     
     
       10. The method of  claim 9 , further comprising:
 determining at least one metric of reception activity of the device; and 
 determining the polling of the access point of the wireless network based at least in part on the at least one metric of reception activity. 
 
     
     
       11. The method of  claim 9 , further comprising:
 receiving a response from the access point that data is to be transmitted to the device; and 
 waking up based at least in part on the received response and remaining in the awake mode until elapse of the determined inactivity time interval. 
 
     
     
       12. The method of  claim 9 , further comprising:
 receiving a response from the access point that no data is to be transmitted to the device; and 
 returning to the sleep mode based at least in part on the received response. 
 
     
     
       13. The method of  claim 12 , further comprising:
 receiving another response from the access point that no data is to be transmitted to the device; 
 returning to the sleep mode based at least in part on the received another response; and 
 discontinuing the polling of the access point based at least in part on the receiving of the response and the another response. 
 
     
     
       14. The method of  claim 1 , further comprising:
 determining a value Q D  for the determined inactivity time interval as a ratio of throughput during a power duty cycle of the device to the power duty cycle; 
 comparing the determined value Q D  to a reference value Q REF ; and 
 adjusting an inactivity time interval for the subsequent awake interval based at least in part on a result of the comparing. 
 
     
     
       15. The method of  claim 14 , wherein adjusting the inactivity time interval for the subsequent awake interval comprises:
 increasing the inactivity time interval for the subsequent awake interval when the determined value Q D  is greater than the reference value Q REF ; and 
 decreasing the inactivity time interval for the subsequent awake interval when the determined value Q D  is less than the reference value Q REF . 
 
     
     
       16. An apparatus for adapting an inactivity time interval for a device in a wireless communications network, comprising:
 means for communicating with an access point of the wireless communications network during awake intervals in which the device is in an awake mode; 
 means for determining a running average of at least one channel congestion metric of at least one channel of the wireless network during a first awake interval of the awake intervals; 
 means for determining, for at least one awake interval of the awake intervals, an inactivity time interval for remaining in the device awake mode after at least one uplink or downlink transmission of the at least one awake interval based at least in part on the determined running average of the at least one channel congestion metric; and 
 means for adjusting the inactivity time interval for the device for at least one from the group consisting of: 
 the first awake interval, and 
 a subsequent awake interval. 
 
     
     
       17. The apparatus of  claim 16 , further comprising:
 means for entering a sleep mode after an elapse of the determined inactivity time interval; and 
 means for polling the access point of the wireless network during a sleep mode interval to determine if data is to be transmitted to the device from the access point. 
 
     
     
       18. The apparatus of  claim 16 , further comprising:
 means for determining a value Q D  for the determined inactivity time interval as a ratio of throughput during a power duty cycle of the device to the power duty cycle; and 
 means for comparing the determined value Q D  to a reference value Q REF , 
 means for adjusting an inactivity time interval for the subsequent awake interval based at least in part on a result of the comparing. 
 
     
     
       19. A computer program product for adapting an inactivity time interval for a device in a wireless communications network, the computer program product comprising a non-transitory computer readable medium, the computer readable medium storing instructions executable by a processor to:
 communicate with an access point of the wireless communications network during awake intervals in which the device is in an awake mode; 
 determine a running average of at least one channel congestion metric of at least one channel of the wireless network during a first awake interval of the awake intervals; 
 determine, for at least one awake interval of the awake intervals, an inactivity time interval for remaining in the device awake mode after at least one uplink or downlink transmission of the at least one awake interval based at least in part on the determined running average of the at least one channel congestion metric; and 
 adjust the inactivity time interval for the device for at least one from the group consisting of: 
 the first awake interval, and 
 a subsequent awake interval. 
 
     
     
       20. The computer program product of  claim 19 , wherein the instructions are executable to:
 enter a sleep mode after an elapse of the determined inactivity time interval; and 
 speculatively poll the access point of the wireless network during a sleep mode interval to determine if data is to be transmitted to the device from the access point. 
 
     
     
       21. The computer program product of  claim 20 , wherein the instructions are executable to:
 determine at least one metric of reception activity of the device; and 
 determine the speculative polling the access point of the wireless network based at least in part on the at least one metric of reception activity. 
 
     
     
       22. The computer program product of  claim 20 , wherein the instructions are executable to:
 receive a response from the access point that data is to be transmitted to the device; and 
 wake up based at least in part on the received response and remaining in the awake mode until elapse of the determined inactivity time interval. 
 
     
     
       23. The computer program product of  claim 19 , wherein the instructions are executable to:
 determine a value Q D  for the determined inactivity time interval as a ratio of throughput during a power duty cycle of the device to the power duty cycle; 
 compare the determined value Q D  to a reference value Q REF ; and 
 adjust an inactivity time interval for the subsequent awake interval based at least in part on a result of the comparing. 
 
     
     
       24. The computer program product of  claim 23 , wherein the instructions for adjusting the inactivity time interval for the subsequent awake interval are executable to:
 increase the inactivity time interval for the subsequent awake interval when the determined value Q D  is greater than the reference value Q REF ; and 
 decrease the inactivity time interval for the subsequent awake interval when the determined value Q D  is less than the reference value Q REF . 
 
     
     
       25. An apparatus for wireless communication comprising:
 a processor; 
 
       a memory coupled to the processor; wherein the processor is configured to cause at least one device to:
 communicate with an access point of the wireless communications network during awake intervals in which the device is in an awake mode; 
 determine a running average of at least one channel congestion metric of at least one channel of the wireless network during a first awake interval of the awake intervals; 
 determine, for at least one awake interval of the awake intervals, an inactivity time interval for remaining in the device awake mode after at least one uplink or downlink transmission of the at least one awake interval based at least in part on the running average of the at least one channel congestion metric; and 
 adjust the inactivity time interval for the device for at least one from the group consisting of: 
 the first awake interval, and 
 a subsequent awake interval. 
 
     
     
       26. The apparatus of  claim 25 , wherein the processor is further configured to cause the device to:
 enter a sleep mode after an elapse of the determined inactivity time interval; and 
 speculatively poll the access point of the wireless network during a sleep mode interval to determine if data is to be transmitted to the device from the access point. 
 
     
     
       27. The apparatus of  claim 25 , wherein the processor is further configured to cause the device to:
 determine a value Q D  for the determined inactivity time interval as a ratio of throughput during a power duty cycle of the device to the power duty cycle; 
 compare the determined value Q D  to a reference value Q REF ; and 
 adjust an inactivity time interval for the subsequent awake interval based at least in part on a result of the comparing.